Programmed spindle speed

ABSTRACT

An improved method and apparatus for programming the slowdown period of a yarn overend winding apparatus including draw rolls and a spindle wherein the draw roll and spindle are programmed in relationship to each other until the draw rolls reach a set predetermined low speed and then the spindle is brought to rest after the draw rolls have become stationary.

United States Patent Williams 1 Feb. 1,1972

[54] PROGRAMMED SPINDLE SPEED [72] Inventor: David M. Williams,Greenville, S.C.

[73] Assignee: Fiber Industries, lnc.

[22] Filed: Nov. 7, 1969 I21 Appl. No.: 874,742

[52] U.S.Cl. ..57/93,57/55.5, 57/157 S, 242/261 [51] Int. Cl ..D0lh1/26, D01h 1/36 [58] Field of Search ..57/88, 34, 55.5, 66, 75, 78,

[56] References Cited UNITED STATES PATENTS 3,358,433 12/1967 Curtis etal. ..57/93 3,472,014 10/1969 Taylor et al ..57/93 3,488,938 1/1970Johnson et al.. .....57/98 3,521,441 7/1970 Lamparter ..57/93 X3,526,244 9/1970 .loy ..57/93 X Primary Examiner-John PetrakesAttorney-Thomas J. Morgan, S. D. Murphy and Louis Gubinsky [5 7]ABSTRACT An improved method and apparatus for programming the slowdownperiod of a yarn overend winding apparatus including draw rolls and aspindle wherein the draw roll and spindle are programmed in relationshipto each other until the draw rolls reach a set predetermined low speedand then the spindle is brought to rest after the draw rolls have becomestationary.

10 Claims, 4 Drawing Figures PATENTEB FEB H972 3,53

sum 1 or 4 I nvenlora oAvlb M. WILLIAMS BYULW A llorney;

PATENTED FEB H972 3IQ3 L414 SHEET '8 BF 4 740/0 AC. DRAW m/ws MOTOR was%f FORMER 570p BRAKE [0W SPHD RfFfPf/K' POE/VHO I (AM METER CONTROLInvenlors DAVID M. WILLIAMS 'By (9W i Atlorneys PROGRAMMED SPINDLE SPEEDBACKGROUND OF THE INVENTION This invention relates to a method andapparatus for winding yarn packages especially of synthetic polymericfilaments or yarns, and is particularly concerned with the collection ofsuch filaments in the form of packages on bobbins mounted on rotatingspindles, in conventional drawing apparatus, or other forms of overendwinding apparatus of the kind in which the filaments are fed to thespindles via rotating processing rolls, and the completed packages arebrought to rest before being doffed, and the empty bobbins are broughtfrom rest up to an initial operable rotational speed after the filamentshave been secured thereto for rotation therewith.

The term apparatus of the kind specified, will-be used hereinafter torefer to such apparatus.

Overend winding apparatus may, for example, have a ringand-travelleryarn guide around each spindle, or comprise cap-spinning apparatus; butfor convenience in describing the invention in this specification itwill be assumed that the apparatus has a ring-and-traveller yarn guide,although it must be understood that the present invention applies alsoto other forms of overend winding apparatus. The package produced bysuch apparatus will usually be tapered in form.

Further, for convenience in this specification, the roll or cooperatingrolls, which engage the running filament immediately before it iscollected on the package, will be referred to hereinafter and in theclaims as the draw rolls, although as indicated above, the presentinvention is applicable to various kinds of apparatus other than drawingapparatus. By drawing" we mean that a filament of synthetic polymericmaterial is stretched to cause the molecules to orientate themselvesalong the filament axis, thus increasing the tenacity of the filament.

The filament may pass between the nip of two cooperating draw rolls, orbe wrapped around a single roll, or around a pair of cooperating rollscomprising a rotating roll and separator roll, which latter may berotating or stationary.

The winding apparatus may include programming means arranged to vary thespeed of the spindle throughout the major part of the winding of eachpackage, for some particular purpose; and the present invention isparticularly, but not exclusively, concerned with such overend windingapparatus in which it is possible so to vary the value of the spindlespeed according to a desired program.

In overend winding apparatus, it may be shown that the spindle speed isequal in magnitude to the traveller speed plus the winding-on speed ofthe filament, this latter term being the fraction of spindle speedcorresponding to the winding-on of the filament, and being equal inmagnitude to the spindle speed if the traveller is stationary.

Thus, it is possible to control some feature of the winding operationwhich is related to winding-on speed and traveller speed throughout theproduction of a package, in order to obtain some desired object, byemploying a suitable spindle speed program.

In any such spindle speed program, the traveller speed should not, underknown conditions, be allowed to exceed about 8,000 r.p.m., excepttransiently, otherwise the yarn guide device will be subjected toexcessive stresses, and unacceptable wear and breakage will ensue.

Further it is desired that a stable package be produced; and thus it isessential that the filament be tensioned to an extent above a certainminimum value so that a stable balloon be maintained, and the manner ofthe lay of the filament on the package be predicted, and the filamentsarranged to be securely laid on the package and not tending to sloughoff it.

Thus, the rotating traveller is used to tension the running filament tothe requisite amount in order that a stable balloon may be obtainedthroughout the winding operation, the balloon being tensioned to anamount of at least 0.l grams per denier in the case of a polyamidefilament, and the spindle speed is so programmed that the travellerspeed is held within a predetermined narrow range of values.

It is particularly desirable that this condition should be maintainedduring the startup and slowdown periods in the formation of eachpackage, because, due to the reasons given above, such a condition willreduce the propensity of the filament to break during these periods(filament breakages being more likely to occur at these periods in thepackage-winding cycle, than intermediate therebetween).

The present invention is concerned with obtaining such a windingcondition while the winding machine is slowing down, by the provision ofpositive programming means arranged to control the spindle speed duringthis period. During this period also, loops tend to be formed on thepackage, if filament breakages are avoided, and the spindle speedprogram during this period is therefore arranged to be such that bothkinds of irregularities in the winding operation are reduced.

Slowdown breakages occur when the spindle rotational speed is reduced ata faster rate than is desired in relation to a given draw rolldeceleration, with consequent overfeeding of the filament from thedraw-rolls to the spindle causing an uncontrollable balloon to beproduced. Thus, the filament may eventually lick back onto the drawrolls, or become entangled and snagged either with itself or on parts ofthe winding apparatus, and so break.

However, if the spindles are allowed to run on by an excessive amount,or the draw rolls are braked too quickly, then the twist insertion ratein the balloon rises, and this twist runs back to the draw rolls, and aso-called slowdown loop will occur. Increase in the twist insertion rateoccurs because, in the dynamic state, the form of the balloon willremain substantially constant. Thus, if the filament delivery speed,i.e., draw roll speed, is reduced sharply, the winding-on speed mustreduce in proportion. However, if the spindle speed maintains the samevalue, the traveller must accelerate to compensate for the reducedwinding-on speed, until when no filament is being delivered, then noneof the filament is wound onto the package and the balloon will speed upuntil its rotational speed is equal to that of the spindle. Thisincrease in traveller speed and reduced winding-on speed accounts forthe increase. in the twist insertion rate.

The increased twist runs back up the filament and may cause a wrap ofthe filament to slip off the draw rolls, when these comprise acooperating draw roll and separator roll. The sudden concomitantincrease in the amount of filament in the balloon will cause a completeyarn loop to be wound onto the package.

It will be appreciated that it is relevant to such loop formationwhether S or Z twist is being inserted into the filament, because, in agiven form of winding arrangement, the insertion of one direction oftwist will tend to keep the wraps on the draw rolls, while the insertionof the other direction will tend to cause the wraps to roll off the drawrolls.

Single-filament loops may, however, be caused in the threadline even ifcomplete yarn loops are not produced; and these single-filament loopsare equally prejudicial to the usage of the yarn.

The existence of any slowdown breakages and loops will result in thepackages sold being slightly below standard weight (because the portionof the filament with loops will have to be stripped from the packageduring inspection), if as usual it is intended that the portion of thefilament processed during the slowdown operation of the windingapparatus should form part of the package. If slowdown breakages andloops can be eliminated, it will obviate the need for packages to besuperficially inspected, and so cause a reduction in operation costs.

With respect to the production of standard weight processed packages, itwill be appreciated that winding apparatus having a programmed windingprocedure, and in particular a programmed slowdown procedure, will beless likely to suffer from between doff variations in the windingoperation, and hence there is less likelihood of uncontrollablevariations in package weight occurring, compared to winding apparatuswhich is not controlled in such a positive manner.

It is of importance not to produce packages of below standard weight dueto unintentional breakages occurring, or due to the formation of loops,because of their possible unsuitability for use in subsequentmanufacturing processes. Further, there will be a high wastage rate ifthe filament wound thereon is to be used in specified discrete amounts,because the amount of the filament remaining on he supply package willbe considerably more than was intended after, say, processed packages ofa specified weight have been wound therefrom.

This wastage of the filament will be particularly important if heavydenier yarns are being processed on the machine, which yarns usually aredesired to have as high a throughput rate as possible and have arelatively shorter package-winding cycle.

The presence of loops in the package will also cause package instabilityat their locations and this will cause a transient relatively largereduction in the takeoff tension of the filament at this point whenunwinding the filament from the package. The package will, therefore, beunsuitable for use on a creel where the filament of one package isconnected to the filament of an adjacent package.

Hence, it will be appreciated that, it is important to be able topredict precisely the slowdown procedure for the winding apparatus, andthe spindle speed program should be such that there is avoidance both ofslowdown breakages due to the spindle speed decaying too quickly, and ofslowdown loops due to the spindle running on more than was intended. Itmay be possible according to this invention to arrange the slow-' downwinding conditions such that both these faults can be eliminated; but inany event a compromise solution can be adopted so that the optimumwinding condition for minimum slowdown breakage rate and loop formationrate are obtained.

If such optimum conditions are attempted to be employed in windingapparatus not having positive programming means, it is found that themanner of operation of the apparatus requires constant observation inorder that the critical conditions be maintained, and the controllingelements of the apparatus require constant trimming to preserve thedesired manner of operation, particularly if the slowdown period isinitiated when the package rotational speed is relatively high and thepackage being wound is relatively large.

In order to reduce or eliminate the above problems associated with theslowdown sequence of an overend yarnwinding process, it has beensuggested to program the slowdown period of the draw-roll-windingapparatus so that spindle speed is controlled in a predeterminedrelationship to the speed of the draw rolls until the draw rolls havebecome stationary and then applying the full spindle brakesimultaneously with draw roll stoppage to bring the spindle to rest assoon as possible within machine capability.

The aforementioned type of slowdown sequence as well as .similarprocedures, have been found to be deficient for a number of reasons, themajor one being the high degree of reliance placed upon the spindlebraking mechanism during the stopping sequence. It is apparent that assoon as the draw rolls have reached standstill, the spindle must becomestationary almost immediately in order to prevent yarn breakage andmaintain the desired threading of yarn over the various rolls and guidesfor startup. The only control allowed the operator with such a system isadjustment of spindle braking force which requires constant observationof the machine. As the spindle brakes become worn, i.e., less efficient,because of repeated usage, the spindle runs on excessively causing aslowdown loop" in the dynamic state and poor control of balloon tensionthrough to complete machine stoppage. Instead of the yarn being threadedthrough the traveller in machine startup condition, the yarn must becompletely restrung from the supply package through the various guidesand over the various rolls to the spindle. Obviously, the linear lengthof yarn wastage is also markedly increased.

Therefore, it is an object of the present invention to provide animproved slowdown sequence for overend yarn winding apparatus.

Another object of this invention is to provide a slowdown sequence foroverend yarn winding apparatus including draw rolls and a spindlewherein means is provided to compensate for changes in spindle brakeefiiciency.

A further object of the invention is to provide programming apparatusfor carrying out the above slowdown sequences.

Still another object of the invention is to provide yarn overend windingapparatus and process which will reduce the number of slowdown filamentbreakages and loops while producing, consistently and reliably,satisfactory standard weight tapered packages which include the portionof the filament processed while the apparatus is slowing down.

Other objects of the invention will be obvious to those skilled in theart from the detailed description of the invention hereinafter.

SUMMARY OF THE INVENTION In accordance with the invention, it has nowbeen found that the slowdown sequence of the full package-winding cycleof a yarn overend winding apparatus can be controlled to reduce slowdownbreakages and loops while leaving the yarn properly strung for machinestartup by a process which comprises positively forwarding yarn by drawrolls to a rotating spindle for winding thereon in the form of a yarnpackage; programming the slowdown period of the full package-windingcycle in such a manner that the spindle speed is positively controlledin a predetermined relationship to the speed of the draw rolls duringthe first part of said period until the draw rolls reach a lowpredetermined speed and thereafter regulating the time of application ofmaximum spindle brake so that said spindle becomes stationary after saiddraw rolls with the yarn maintained under a predetermined tension.

Further, it has been found that the process of the invention can becarried out by an overend winding apparatus of the kind in which yarn isfed to a rotating spindle from processing rolls, said apparatusincluding:

a. a motor adapted to drive the spindle,

b. a second motor adapted to drive the draw rolls independently of thespindle,

c. programming means for controlling the winding operation of theapparatus in a positive manner at least during the slowdown period ofthe full package-winding cycle, said means including a servo deviceforcontrolling the spindle drive motor, a first tachogenerator for thespindle and a second tachogenerator for the draw rolls, and a referenceerror unit adapted to compare electrical signals produced by saidtachogenerator-s during said slowdown period and to feed a resultantelectrical signal therefrom to said servo device, and

d. a low-speed sensing device adapted to receive electrical signals fromsaid second tachogenerator and to activate said servo device to stop thespindle drive at a predetermined time after sensing a predetermined lowspeed from said second tachogenerator.

DESCRIPTION OF THE DRAWING DETAILED DESCRIPTION OF THE INVENTION Inconventional draw-twisting apparatus for synthetic polymeric filaments,such as polyamide, polyester, cellulose ester, polyacrylonitrile orpolyolefin filaments, there are included two or more pairs or sets ofcooperating rolls, each pair I of rolls being arranged to impart adifferent speed to the filament, causing the filament to be drawnbetween two adjacent pairs of rolls, (and, optionally to relax betweenanother two adjacent pairs of rolls).

Snubbing devices, which impose a substantial restraint on the runningfilament, may be included in the apparatus, so that there may be asingle drawing zone or several such zones, and possibly also regions inwhich the yarn may relax or be subjected to some other treatmentprocess. The first pair of rolls which engage the yarn are feed rollsfor the apparatus, and between these and the final pair of rolls, whichare positioned immediately before the winding apparatus, and which areherein referred to as draw rolls," the filament is stretched to manytimes its original length.

Thus, as shown in FIG. 1 a polyamide filament l is withdrawn from acheese 3 mounted on a container 5, and passes through yam guide means 7,9, ll, 13 to a pair of cooperating nip rolls 15, 15 From these niprolls, which serve as positive feed rolls, the filament is wrappedaround an inclined snubbing pin 17, which causes a considerable physicalrestraint to be imposed on the filament resulting in the filamentnecking" and being stretched to, say five times its original length. Thefilament then passes around draw roll 19 with its inclined separatorroll 21, which rolls, which forward the filament to a balloon guide 23and thence to winding apparatus. I

The winding apparatus comprises a vertically extending spindle 25 onwhich a tube 27 for the yarn package 29 is rotatable mounted, and aroundwhich spindle yarn guide means is disposed for causing the filament tobe laid on the package. The yarn guide means is in the form of aconventional ring 31 and traveller 33 device mounted on a ring rail 35,this ring rail being reciprocated along the spindle axis by a known formof builder mechanism, including a stricker plate 37 secured to the ringrail for reciprocation therewith. At each end of each reciprocationstroke the plate is arranged to operate a microswitch (not shown) and socause reversal in the direction of movement of the ring rail. Thepositions of the microswitches are controlled respectively by two camsrotatably mounted on a shaft driven at a constant speed.

The main drive means for the draw twist machine comprises an ACinduction motor coupled to each of the feed rolls and the draw rolls ofthe machine, but not to the spindles on which the packages are beingformed, the spindles being arranged to be driven by a separate DC motor.

Thus, the drive means of the draw twist machine is in two parts, andhence both the spindles and the draw rolls can be allowed to accelerateand decelerate independently of each other during the startup andslowdown periods of each package winding cycle.

In order that filament breakages shall be avoided during the startupperiod of each package winding cycle, an electrical timer is included inthe winding apparatus, this timer being arranged so that the draw rolls(and the feed rolls) are not driveably connected to the AC motor untilafter the spindles have been driveably connected to the DC motor. Thesetting of the timer is adjustable manually.

The criteria upon which the optimum value for the delay period instarting the AC motor after the DC motor is determined are set outbelow.

It is essential that a stable balloon be maintained as soon as the drawrolls have started to rotate and the filament is being wound on thepackage, and consequently, it is important that the traveller speed bemaintained within a certain range during this latter part of the startupperiod, when the draw rolls are rotating.

Although the traveller speed of the yarn guide should at no time duringthis period be permitted to exceed the highest speed of the range, itshould start at this speed when the draw rolls have started to rotate,or rise to it soon after they have started to rotate. As a result thetraveller speed will then fall to a value near to its minimum acceptablespeed when the draw rolls have obtained their maximum speed.

in this way the balloon tension is given its maximum possible valueinitially, which is found to cause a reduction in the number of filamentbreakages. The spindles are arranged to obtain their maximum speed,i.e., their requisite speed according to the winding program at the endof the startup period, either at the same time as or before the drawrolls have obtained their corresponding maximum speed.

During the startup period in each package winding cycle, it is usual toarrange for a waste bunch to be wound, particularly as the filament atthis point may be inadequately drawn or otherwise processed.

The time taken for the draw rolls to be brought up to speed should be asshort as possible, for productivity reasons, and such that the wastebunch, which is wound during this time, is not too large.

Throughout the major part of the winding operation, when the windingapparatus is operating in a normal manner, the AC motor is arranged todrive the draw rolls at a constant speed, which speed is related to thedesired processing speed for the apparatus.

However, the DC motor is arranged to drive the spindles according to apredetermined winding program during this period, in order that somedesired object, with respect to the winding operation, may be obtained.

Thus, the spindle speed can be arranged to be varied throughout thewinding of a package in accordance with the profile of a cam embodyingthe desired spindle speed program.

The DC motor driving the spindles is arranged to be controlled by aservo device, which in turn is controlled by the cam, this cam beingarranged to be rotated at a constant speed by being rotatably mounted onthe shaft comprising the ring rail traverse cam drive means.

The servocontrol device for the DC motor comprises a three-phasemagnetic amplifier, the input of which is controlled by a preamplifier.The motor armature voltage comprises the output from the magneticamplifier, and the current from a rectifier positioned across one phaseof the electrical supply to the device comprises the shunt fieldexcitation current for the motor.

The programming cam is used to produce a reference signal, which variesin accordance with the winding program, and the spindle speed ismonitored continuously by means of the first tachogenerator operablycoupled to the output shaft of the DC motor. The reference error unitcompares the signal from the first tachogenerator with the referencesignal.

The error signal obtained by this comparison is then used to alter theoutput of the DC motor by being fed to the preamplifier of theservocontrol device and so alters the magnitude of the current fed tothe armature of the motor.

The cam follower comprises the slider of a linear potentiometer, and theoutput from this potentiometer is the reference signal.

Trimming rotary potentiometers are provided at each end of the linearpotentiometer of the programming means, each such rotary potentiometerhaving a range approximately 20 percent of the linear potentiometerrange and being used to control the effective range of the linearpotentiometer.

[t is essential that the balloon tension be maintained within a similarnarrow range of value during the slowdown period also, so that breakagesmay be reduced or avoided during this period.

The optimum slowdown conditions required to be reproduced by the windingapparatus in winding a yarn of 40 denier polyhexamethylene adipamide,for instance, are that the traveller speed shall not fall below 2,500rpm. while the draw rolls are rotating and the filament is being woundin order that a stable balloon may be maintained and that the spindlesshall be brought to rest as soon as practicable after the draw rollswhereby there will be reduction in the number of filament breakages andloops.

Due to the relatively high inertia of the motors coupled respectively tothe spindles and the draw rolls, both the spindies and the draw rollswill tend to run on when the motors are deenergized, and in any eventthey will decelerate at rates which are independent of each other.

Thus, at the start of the slowdown period, the AC motor driving the drawrolls may be switched off so that the draw roll speed is allowed todecay normally. Preferably, a draw roll braking means is employed.

In order that there should be the controlled predetermined relationshipbetween the spindle speed and the draw roll speed during the first partof the slowdown period the second tachogenerator is provided to monitorthe speed of the draw rolls, and during the first part of the slowdownperiod, the output signal from this second tachogenerator is fed to thereference error unit.

The connection of the second tachogenerator to the reference error unit,and the disconnection of the program cam potentiometer therefrom, iscaused by the programming means upon the transference of the windingapparatus from its normal operating procedure to its slowdown procedure.(Compare FIGS. 3 and 4) The reference error unit compares this signalwith that from the first tachogenerator monitoring the spindle speed,and feeds back a signal to the DC motor to drive it, so that the twomotors slow down at a predetermined ratio.

The programming means causes another signal to be compounded with theabove-mentioned signal, the magnitude of which second signal is suchthat, alone, it would cause the spindles to be driven at above theminimum value of, say, 2,500 r.p.m.

This second signal is produced by a traveller speed potentiometer whichis positioned across a fixed voltage. When the apparatus is idle, thispotentiometer is adjusted to give the desired voltage, determinedempirically previously, and the programming means places thispotentiometer across the first tachogenerator, which is coupled to theDC motor drive shaft, when the slowdown procedure is initiated. Thissecond signal can be eliminated by adjusting the spindle brake means toallow a minimum spindle speed at time of draw roll stop by comparisonthrough the reference unit.

The above-referred-to program for the slowdown period of the packagewinding cycle is shown graphically in FIG. 2, in which the full linesindicate the actual speed/time programs of the spindle and draw rollsrespectively.

In order to ensure that, when the winding apparatus changes over fromthe normal operating procedure to the slowdown procedure, there is nosuddenjump in the DC motor speed or traveller speed, and the windingapparatus begins smoothly to slow down, there is provided a changeoverspeed" potentiometer positioned across the second tachogenerator, i.e.,that which is operably coupled to the draw rolls. During the initialsetting up of the apparatus, with the apparatus running, and the spindlespeed arranged to be the value at which the slowdown procedure is to beinitiated, this potentiometer is adjusted so that no signal is fed fromthe second tachogenerator to the reference error unit.

As already mentioned, in order that a positive control may bemaintained, it is advantageous to arrange that the spindles are drivenagainst lightly applied braking pressure during the first part of theslowdown period.

Thus, upon the transference of the winding apparatus from its normaloperating procedure to its slowdown procedure, the programming means isarranged to actuate the spindle brake means, and during the initialsetting up of the winding apparatus, with the apparatus operating andwith the brake means in this position, this means is adjusted so thatthe DC motor armature current is at a low, finite, but detectable value.Hence, the spindle drive means will not hunt during the first part ofthe slowdown period.

The low-speed sensing device coupled to the second tachogenerator isarranged also to control the spindle-braking means. The arrangement issuch that, when the sensing device detects that the secondtachogenerator is registering a predetermined low speed for the drawrolls, the sensing device causes the spindle-braking means to beactuated to cause maximum braking restraint to be applied to thespindles at a predetermined time after said low speed is reached tobring the spindle to rest after the draw rolls have become stationarywith proper tension on the yarn through to the spindle, which is thecondition required to avoid the occurrence of slowdown loops on thepackage being wound. In this manner, needed flexibility is incorporatedinto the programmed slowdown sequence. By allowing adjustment of time ofmaximum spindle brake application in conjunction with control of brakingforce, the aforementioned disadvantages, particularly variation inballoon tension and degree of draw at standstill, are markedly reduced.With the present invention, the machine is stopped with the yarn inposition for the startup sequence. Restringing, which accounts for themajor employee cost of the draw-twisting operation is limited tosevering the yarn past the traveller, removing the full package andinserting a new pim on the spindle. An additional advantage arises fromthe fact that the yarn is fully drawn through to the traveller whichreduces yarn breaks upon startup because of the increased strength ofthe drawn yarn.

The sensing device is also operably coupled to the spindle drive meansservo device during the slowdown period, and upon the activation of thebraking means by the sensing device, the sensing device simultaneouslycauses the deenergization of the DC motor driving the spindles. Thus,there is nothing counteracting the torque applied by the braking meanson the spindles.

Thus, during the slowdown period in each package-winding cycle, themanner of operation of the DC motor is positively programmed so as toavoid the occurrence of both filament breakages and loops during thisperiod.

A second variable timer is included in the apparatus so that themovement of the ring rail of he winding apparatus is controlled duringthe slowdown period. It is important that the ring rails should not bebrought to rest before the slowdown bunch has been wound onto thebobbin. Thus, by use of this second timer, the ring rail is stopped at apredetermined time after the initiation of the slowdown program, thisdelay being such that the ring rail is stopped after the draw rolls havestopped. The spindles tend to run on after this time, even under maximumbraking forces, particularly if relatively large packages are beingwound at relatively high speeds.

According to the present invention, the following operating conditionswere employed during the slowdown sequence for a draw twist machinedrawing 40 -denier polyhexamethylene adipamide yarn having 13constituent filaments, the machine operating at a drawing speed of 4,200feet per minute.

SLOWDOWN SEQUENCE At the termination of the full package build cycle asdetermined automatically by the particular programmed means em ployed,the slowdown sequence is initiated. Simultaneously (as graphicallydepicted in FIG. 2 of the drawing), the draw roll motor is deenergized,the draw rolls are braked so that they reach a stationary position froman initial speed of about 4,200 r.p.m. in an approximate preset time,for example 20 seconds, and a partial spindle brake is applied againstthe driven spindles rotating at about 8,000 r.p.m. As the draw rollsdecelerate, draw roll and spindle speeds are continuously monitored andfed into the reference error unit which programs the spindle speed downin preset relationship to draw roll deceleration. When the draw rollsdecelerate to the predetermined low speed, for example 1,000 r.p.m., thespindle motor is deenergized and maximum spindle brake is applied at aset time thereafter to stop the spindle with adequate tension on theyarn and minimum run-on after the draw rolls have become stationary. Forexample, the spindle brake is set so that the spindle is rotating at apredetermined speed, for example 3,0003,500 r.p.m., when the draw rollshave stopped.

The spindle is then brought to stop 3-5 secondsafter the draw rolls stopand the slowdown sequence is terminated about 24 seconds after theinitiation thereof. In practice a separate timer lowers the ring rail ofthe ring and traveller apparatus about 1-2 seconds before the draw rollsstop so that adequate but minimum waste yarn is wound about the wastewhorl.

In addition to the elimination of filament breakage during the slowdownperiod and reduction in slowdown loops to below 1 percent, the yarn isdrawn and under tension suitable for start up.

The accuracy with which the predetermined startup and slowdown programwas reproduced by the apparatus described above was i k percent, whichwas the accuracy of the motors employed. This was found to be adequateand the beneficial effects, referred to above as being obtainable by useof the apparatus according to the present invention, were found.

In practice, it is found that there is a range of several seconds, i.e.,3-5, during which the spindles may come to rest, for a given slowdownperiod for the draw rolls, and in which range neither slowdown breakagesnor loops occur. At speeds above 8,000 rpm, the traveller becomessubject to excessive stresses, and this speed was therefore neverexceeded.

ln operation, the spindle brake was found not to need readjustment overa considerable period of operation of the machine while in conventionalequipment of this type the spindle brake would require resetting atintervals of approximately 3 months.

It will be appreciated that the quality of yarn packages produced onapparatus according to the invention will be improved, and the yarnwound thereon will have greater uniformity, compared with what has beenpossible heretofor without an excessively high wastage rate associatedwith each machine.

In addition, the apparatus allows for considerable flexibility in themanner in which it may be used, while still being capable of giving thebenefits occurring from the use of the present invention. The use of twocontrol means, time of application of maximum spindle speed brake aswell as control of braking force, give this increased flexibility incomparison with the process rigidity present when the time controlcomponent is absent, i.e., maximum spindle brake is always applied atdraw roll stoppage.

It is understood, of course, that various changes may be made in theinvention which will be obvious to those skilled in the art. Forexample, the invention may be employed with all types of continuousyarns, including spun staple yarn, such as polyamides, polyesters,polyacrylonitriles, polyolefins, polyurethanes, polycellulosics, etc.Additionally, between startup and slowdown sequences, the package buildmay be entirely controlled by a preset cam arrangement which regulatesspindle speed in accordance with a predetermined program as opposed tothe continuing monitoring of the feedback system of the drawing and theoperation need not be lagged, i.e., continuous filaments could be feddirectly from the extrusion apparatus to the draw twister.

lclaim:

l. A method of winding a yarn package on yarn overend winding apparatusin a manner to reduce slowdown breakages and loops, while leaving theyarn properly strung and drawn for machine startup, which comprises:

a. positively forwarding yarn by draw rolls to a rotating spindle forwinding thereon in the form of a yarn package;

b. programming the slowdown period of the full packagewinding cycle bypositively controlling spindle speed in a predetermined relationship tothe speed of the draw rolls during the first part of said period untilthe draw rolls reach a low predetermined speed;

c. thereafter regulating the time of application of maximum spindlebrake so that said spindle becomes stationary after said draw rolls withthe yarn maintained under a predetermined tension; and

d. stopping said draw rolls independently of said spindle when a fullyarn package has been wound and bringing said spindle to rest after thedraw rolls have become stationary.

2. The method of claim 1 wherein said yarn is a polyamide.

3. The method of claim 1 wherein said yarn is a polyester.

4. The method of claim 1 wherein said yarn is a polyolefin.

5, The method of claim I wherein said yarn is a polyacrylonitrile.

6. The method of claim 1 wherein the startup period of the fullpackage-winding cycle is also programmed in a predetermined manner.

7. The method of claim 1 wherein the portion of the full winding cyclebetween startup and slowdown sequences is programmed in a predeterminedmanner.

8. The process of claim 1 wherein said draw rolls are driven at aconstant speed during said full package-winding cycle and the spindle isdriven separately therefrom according to a predetermined program.

9. Overend winding apparatus of the kind in which yarn is fed to arotating spindle from processing rolls, said apparatus including:

a. a motor adapted to drive the spindle;

b. a second motor adapted to drive the draw rolls independently of thespindle;

c. programming means for controlling the winding operation of theapparatus in a positive manner at least during the slowdown period ofthe full package-winding cycle, said means including a servo device forcontrolling the spindle drive motor, a first tachogenerator for thespindle and a second tachogenerator for the draw rolls, and a referenceerror unit adapted to compare electrical signals produced by saidtachogenerators during said slowdown period and to feed a resultantelectrical signal therefrom to said servo device; and

d. a low-speed sensing device adapted to receive electrical signals fromsaid second tachogenerator and to activate said servo device to stop thespindle drive at a predetermined time after sensing a predetermined lowspeed from said second tachogenerator.

10. The apparatus of claim 9 wherein said servo device activates atiming device which applies maximum braking force to said spindle at apredetermined time after said activation.

1. A method of winding a yarn package on yarn overend winding apparatus in a manner to reduce slowdown breakages and loops, while leaving the yarn properly strung and drawn for machine startup, which comprises: a. positively forwarding yarn by draw rolls to a rotating spindle for winding thereon in the form of a yarn package; b. programming the slowdown period of the full package-winding cycle by positively controlling spindle speed in a predetermined relationship to the speed of the draw rolls during the first part of said period until the draw rolls reach a low predetermined speed; c. thereafter regulating the time of application of maximum spindle brake so that said spindle becomes stationary after said draw rolls with the yarn maintained under a predetermined tension; and d. stopping said draw rolls independently of said spindle when a full yarn package has been wound and bringing said spindle to rest after the draw rolls have become stationary.
 2. The method of claim 1 wherein said yarn is a polyamide.
 3. The method of claim 1 wherein said yarn is a polyester.
 4. The method of claim 1 wherein said yarn is a polyolefin.
 5. The method of claim 1 wherein said yarn is a polyacrylonitrile.
 6. The method of claim 1 wherein the startup period of the full package-winding cycle is also programmed in a predetermined manner.
 7. The method of claim 1 wherein the portion of the full winding cycle between startup and slowdown sequences is programmed in a predetermined manner.
 8. The process of claim 1 wherein said draw rolls are driven at a constant speed during said full package-winding cycle and the spindle is driven separately therefrom according to a predetermined program.
 9. Overend winding apparatus of the kind in which yarn is fed to a rotating spindle from processing rolls, said apparatus including: a. a motor adapted to drive the spindle; b. a second motor adapted to drive the draw rolls independently of the spindle; c. programming means for controlling the winding operation of the apparatus in a positive manner at least during the slowdown period of the full package-winding cycle, said means including a servo device for controlling the spindle drive motor, a first tachogenerator for the spindle and a second tachogenerator for the draw rolls, and a reference error unit adapted to compare electrical signals produced by said tachogenerators during said slowdown period and to feed a resultant electrical signal therefrom to said servo device; and d. a low-speed sensing device adapted to receive electrical signals from said second tachogenerator and to activate said servo device to stop the spindle drive at a predetermined time after sensing a predetermined low speed from said second tachogenerator.
 10. The apparatus of claim 9 wherein said servo device activates a timing device which applies maximum braking force to said spindle at a predetermined time after said activation. 